Characterization of the contaminant bacterial communities in sugarcane first-generation industrial ethanol production

Abstract

The industrial ethanolic fermentation process is operated in distilleries, either in fed-batch or continuous mode. A consequence of the large industrial ethanol production is bacterial contamination in the fermentation tanks, which is responsible for significant economic losses. To investigate this community, we accessed the profile of bacterial contaminant from two distilleries in Brazil, each operating a different fermentation mode, throughout sugarcane harvest of 2013-2014. Bacterial communities were accessed through Illumina culture-independent 16S rDNA gene sequencing, and qPCR was used to quantify total bacteria abundance. Both ethanol production modes showed similar bacterial abundance, around 105 gene copies/mL. 16S rDNA sequencing showed that 92%-99% of the sequences affiliated to Lactobacillus genus. Operational taxonomic units differently represented belonged mainly to Lactobacillus, but also to Weissella, Pediococcus, Acetobacter and Anaeosporobacter, although in lower abundance. Alpha-diversity only showed a correlation through the fermentation tanks in continuous mode, where it was always higher in the second and third tanks. Beta-diversity clearly separated the two distilleries and metagenome prediction reinforces clusterization within distilleries. Despite certain variations between bacterial community in the distilleries throughout harvest season, Lactobacillus were the main genera reported in both distilleries and bacterial community seemed to persist along time, suggesting bacterial reinfestation.

Dynamics of microbial contaminants is driven by selection during ethanol production

“…The sequences rated as Weissella almost disappeared after the Heater steps (Figure 3). A recent study found lower abundances of Weissella in fermentation tanks,[8] as recorded in this study.…”

“…Consequently, high costs in clean up the equipment arise, reducing the productivity in ethanol production [4–6]. The main contaminant taxon is a Lactobacillus , specifically a Lactic Acid Bacteria (LAB) found in high proportion during the fermentation procedure [7, 8].…”

Desenvolvimento de um método rápido de identificação, ao nível de espécie, de >i<Lactobacillus>/i< e >i<Saccharomyces>/i< em dornas de fermentação, por meio da técnica de MALDI-TOF MS: validação molecular e construção do banco de dados espectral

“…Apesar de certa individualidade de cada processo de produção de etanol e uso de diferentes matérias primas, como milho e cana-de-açúcar, todos trabalhos evidenciaram que os microrganismos contaminantes prevalentes sempre são bactérias ácido lácticas, particularmente do gênero Lactobacillus, representando mais de 40% dos isolados (SKINNER; LEATHERS, 2004;BONATELLI et al, 2017).…”

Avaliação dos efeitos causados por contaminações bacterianas em fermentações etanólicas de primeira geração utilizando metodologias multi-ômicas

“…A grande maioria das bactérias contaminantes de fermentações etanólicas de primeira geração no Brasil são LAB, sendo que entre as espécies mais abundantes destacam-se L. fermentum e L. plantarum (CARVALHO-NETTO et al, 2015;BONATELLI, 2017). Acredita-se que a capacidade de tolerar altas concentrações de etanol e baixos índices de pH sejam algumas das explicações da presença destes microrganismos em fermentações industriais brasileiras (AMORIM et al, 2011).…”

“…Contudo, a aplicação indiscriminada destas práticas envolve um grande aporte de recursos e pode gerar problemas graves para a indústria, espécie humana e meio ambiente (LUDWIG, OLIVA-NETO & ANGELIS, 2001). Carvalho-Netto et al (2015) e Bonatelli et al (2017) mostram que bactérias lácticas e acéticas estão entre os microrganismos mais abundantes do sistema, sendo uma das principais causadoras das perdas de produtividade e geração de estresses bióticos.…”